A study was made of the nature of the thermolabile plasma factors in human blood which promote the phagocytosis of Group A streptococci in vitro in the presence of optimal amounts of type-specific M antibody. The plasmas of individuals with strong opsonic activity (normal) were compared with those of some individuals whose opsonic activity was consistently weak (deficient). A general relationship was established between encapsulation of streptococci and the opsonic requirement for thermolabile plasma factor(s). Marked differences in phagocytosis of Group A organisms by human bloods were demonstrated with encapsulated strains only. Human bloods deficient in the cofactor required for opsonization of encapsulated streptococci (coopsonin) showed a normal rate of phagocytosis against all other organisms and particles studied. Furthermore, coopsonin-deficient bloods contained normal levels of four components of complement, of properdin, of lysozyme, and of direct bactericidal activity against several species of Gram-negative organisms and of E. coli bacteriophage. The independence of the streptococcal coopsonin from complement was also demonstrated by absorption of plasma with bentonite and with zymosan. Under appropriate conditions, the coopsonin was reduced without significant loss of complement. The data support the concept that the capsule of the streptococcus imposes an opsonic requirement for a plasma factor(s) which is present in varying amounts in human bloods and which appears to be independent of the complement system. The possibility that it is accessory to the latter components has not been excluded.

A B STRA CT The relation of seven different M types of streptococci to acute glomerulonephritis associated with skin lesions in South Trinidad has been studied by means of type-specific antibody assays as well as by isolation and identification of the strains. The data indicate that, one after another, five of these strains have prevailed among patients with acute glomerulonephritis during the past five years. At least three of the strains (M-types 55, 49, 57, and/or 60) were associated with epidemic increases in nephritis cases. The appearance of five consecutively predominant types of nephritogenic streptococci during a relatively short period of time is in contrast to the continuing prevalence of M-type 12 strains among nephritogenic streptococci primarily associated with respiratory infections in temperate zones. These observations suggest that the skin sores commonly found on children in tropical Trinidad, provide a particularly suitable environment for development of nephritogenic types. It remains to be seen whether these types will recur or whether new types will continue to emerge in Trinidad.

As the fields of personality and evolutionary psychology merge, new conceptualizations of personality traits will arise. However, individual differences continue to present a recurrent problem for evolutionary psychologists. We contend that the heterogeneity of personality traits provides fitness benefits and fitness costs that relate to fitness outcomes. As these costs and benefits balance one another in the course of individuals' lives, only those traits that create a net positive balance will be correlated with improved fitness outcomes. In this study (N = 155), we showed how extraversion provides positive fitness outcomes to both sexes, suggesting that extraversion creates the best balance of positive and negative characteristics and habits of all of the Big Five. In contrast, other aspects of the Big Five were not related to number of lifetime sex partners, suggesting that the positive and negative aspects of those traits create a near-neutral balance.

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The respiration and growth of 5 strains each of Staphylococcus aureus and Staphylococcus epidermidis in fresh normal rat and rabbit sera were measured. S. aureus grew and oxidized the sera of these animals better than S. epidermidis. Both S. aureus and S. epidermidis grew and respired more actively in rabbit than in rat serum. The antibacterial activity of rat or rabbit serum was stable to heating at 56 °C for 1 h, but its activity was destroyed after heating at 60 °C for 2 h. Treatment of rat and rabbit sera with 0.4 M sodium citrate drastically reduced the antibacterial activity of these sera. Once the sera had been treated with sodium citrate or oxalate, addition of equimolar solutions of calcium chloride or magnesium chloride failed to restore the antibacterial activity of rat and rabbit sera. Addition of ferric ions at concentrations which are not normally found in rat and rabbit sera reversed the inhibitory activity of these sera, thus allowing coagulase-negative strains of staphylococci to grow well in rat and rabbit sera. The antibacterial agent of rat or rabbit serum was absorbed by heat-killed cells of S. aureus and S. epidermidis; treatment with bentonite at a concentration of 100 mg/ml absorbed the antibacterial agent from rabbit serum but only partially from rat serum. The high levels of the antibacterial agent in rat serum may explain the partial removal of this agent by bentonite and may contribute to the marked resistance of the rat to staphylococcal infection.